The Comcast headend in Longview, WA has downconverted the HD Weather Channel feed onto the SD channel (channel 47) which shows an IS2 from nearby Vancouver. I don't quite understand why Comcast is replacing the SD channel with a 4:3 letterboxed HD feed. Perhaps to save money? 
If they've downconverted the HD feed onto an SD channel and removed the HD channel altogether, that's something I've never heard of before. However, repeating the HD feed on the SD channel while keeping the HD channel, too, is becoming a common situation.
Comcast has the regular TWC HD channel in Longview as well, but I wasn't able to view it with the digital adapter box. I guess Comcast must be trying to make room for newer channels by removing the TWC SD feed and repeating the HD feed as they are pretty much the same thing (sort of).